The Nano-Surgeon Always Signals Twice

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Prof. Roy Bar-Ziv and Dr. Lior Nissim. Identifying cancer

 

The search for effective cancer therapies is a lengthy journey fraught with ups and downs: great hopes alternate with disappointing downturns. Research at the Weizmann Institute of Science that is currently in its initial stages might pave the way to a new treatment approach using a miniature genetic device. “We have succeeded in presenting the idea in a test tube,” says Prof. Roy Bar-Ziv of Weizmann’s Materials and Interfaces Department, who headed the research team. “Of course, the human body is so complex compared with isolated cells in a laboratory dish that prolonged studies will be required before this idea can be tested in human beings.”
 
To save the life of a cancer patient, the surgeon must remove the cancerous tumor without harming the surrounding tissue – often a challenging task. Cancer drugs, ideally, must also kill only the tumor cells while sparing the cells that are healthy. Yet, unfortunately, most conventional drugs, along with eliminating the cancer, destroy non-cancerous tissue, producing severe side effects. A new generation of therapies is being designed to kill cancer cells in a targeted, selective manner, reducing unwanted side effects to a minimum.

 
In a study published recently in Molecular Systems Biology, Weizmann Institute researchers synthesized a tiny genetic sensor that identifies cancer cells with great precision and destroys them effectively. The device, a three-gene DNA circuit called a “dual-promoter integrator,” or DPI, performs impressively well in a laboratory dish. Not only does it reliably identify and kill various cancerous cells, it can even assess the “degree” of malignancy, distinguishing between premalignant and full-blown cancerous cells.

 
Yeda Research & Development Company, the Weizmann Institute’s technology transfer arm, has patented the nano-device. Says Bar-Ziv: “We have a long road ahead of us before the genetic sensor can be tried in patients. Our ultimate future vision is for this synthetic sensor to serve as an independent ‘nano-surgeon’ that makes its own decisions, patrolling the body’s tissues, and entering and destroying cancerous cells on the spot.”

 
The DPI “nano-surgeon” identifies the cell as cancerous with the help of two DNA sequences in its circuit. These are two “promoters,” so called because they promote a gene’s activity, determining its timing and levels. For example, some promoters of growth are implicated in cancer: when such promoters are abnormally switched to the ON position more often or with a greater intensity than necessary, the cell turns cancerous. Accordingly, the DPI was designed to measure the activity levels of two such promoters and identify a cell as cancerous when both of them are overly active.

 
When the DPI is inserted into a cell, it responds to its surroundings, mimicking the behavior of the cell’s own genes. If the cell is cancerous and its own promoters are ON, the two promoters in the sensor also switch into an ON position. And once the cell has thus been identified as cancerous, the sensor sends a signal to its third gene – the “killer” gene, which releases a toxic substance eliminating the cell.

 
This relatively simple nano-device has major advantages over existing molecular approaches to the selective destruction of cancer cells. In most cancer gene therapies, malignant cells are identified by only one genetic feature, which often causes healthy cells to be mistakenly targeted for destruction. Using two genetic features makes it possible to identify cancer cells with much greater precision. Moreover, the new synthetic sensor can be “tuned” so that its “killer” gene responds only to signals above a certain level: If even one of the promoters exhibits only weak activity, the sensor will not respond. That in fact is what allowed the scientists to distinguish premalignant cells from cancerous ones: the growth signal in the latter was significantly stronger. Since the difference in growth signal levels between cancerous cells and healthy ones is even greater, this “tuning” can help the “nano-surgeon” to operate efficiently, zeroing in on the cancerous tumor without harming “innocently” growing healthy cells.

 
The research was performed in the laboratory of Prof. Roy Bar-Ziv by Dr. Lior Nissim for his Ph.D. dissertation. Nissim had previously earned a master’s degree in the molecular biology of cancer under the guidance of Weizmann Institute’s Prof. Varda Rotter. Even though the current study focused on cancer, the three-gene sensor, which is built from replaceable modules, might in the future be adapted for the treatment of other diseases or for such screening tasks as the sorting of various stem cells.
 

Prof. Roy Bar Ziv's research is supported by the Phyllis and Joseph Gurwin Fund for Scientific Advancement; and the Carolito Stiftung.

 


 
Prof. Roy Bar-Ziv and Dr. Lior Nissim. Identifying cancer
Life Sciences
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Universal Immunity

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Prof. Zelig Eshhar. New approach to fighting cancer
 
Our immune system has ample weapons for fighting cancer, but of course nobody can win all the battles all the time. As we know only too well, it is often the tumor that gains the upper hand, outsmarting the body’s anti-cancer defenses.
One of the latest attempts to boost these defenses is the so-called adoptive cell transfer, in which patients receive a therapeutic injection of their own immune cells.
 
This therapy, currently being tested in early clinical trials of melanoma and neuroblastoma, has its limitations: Removing immune cells from a patient, not to mention growing these cells outside the body for future reinjection, is extremely expensive and not always technically feasible.
 

Weizmann Institute scientists have now tested in mice a new form of adoptive cell transfer that overcomes these limitations while enhancing the tumor-fighting ability of the transferred cells. The research, reported recently in Blood, was performed in the lab of Prof. Zelig Eshhar of the Institute’s Immunology Department by graduate student Assaf Marcus and lab technician Tova Waks.

The new approach should be more readily applicable than the existing adoptive cell transfer treatments because it relies on a donor pool of immune T cells, prepared in advance, rather than on the patient’s own cells. Moreover, using a method pioneered by Prof. Eshhar more than two decades ago, these T cells are outfitted with receptors that specifically seek out and identify the tumor, thereby promoting its destruction.

In the study, the scientists first suppressed the immune system of mice by a relatively mild dose of radiation; they then administered a controlled dose of the modified donor T cells. The mild suppression temporarily prevented the donor T cells from being rejected by the recipient, but it didn’t prevent the cells themselves from attacking the recipient’s body, particularly the tumor. This attack was precisely what rendered the therapy so effective: while the rejection of the donor T cells was being delayed, these cells had sufficient opportunity to destroy the tumor.

If this method works in humans as well as it did in mice, it could lead to an affordable cell transfer therapy for a wide variety of cancers. Such therapy would rely on an off-the-shelf pool of donor T cells equipped with receptors for zeroing in on different types of cancerous cells.



Proof of Concept



In August 2011, University of Pennsylvania researchers reported in The New England Journal of Medicine that they had successfully used Prof. Zelig Eshhar’s original, adoptive cell transfer approach in a pilot trial of patients with chronic lymphocytic leukemia. The patients were treated with T bodies – genetically engineered versions of their own T cells. “This study has provided a proof of concept for the potency of our T-body therapy: previously shown to work in mice, it has now proved beneficial in cancer patients,” Prof. Eshhar said. “Within three weeks, the tumors had been blown away, in a way that was much more violent than we ever expected,” said senior author Carl June, MD, professor of Pathology and Laboratory Medicine in the University of Pennsylvania’s Abramson Cancer Center, who led the trial. “It worked much better than we thought it would. ”

Encouraged by this initial success, Dr. June and colleagues plan to apply the method to the treatment of other malignancies, including non-Hodgkin lymphoma, acute lymphocytic leukemia and childhood leukemia that is not alleviated by standard family. They also consider using the T bodies in patients with solid tumors, such as ovarian and pancreatic cancer.

 
Prof. Zelig Eshhar’s research is supported by the M.D. Moross Institute for Cancer Research; the Leona M. and Harry B. Helmsley Charitable Trust; the Kirk Center for Childhood Cancer and Immunological Disorders; and the estate of Raymond Lapon.



 
Prof. Zelig Eshhar. New approach to fighting cancer
Life Sciences
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Capturing Cancer

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Prof. Amos Breskin and team. Imaging prostate cancer
 
 
Military intelligence enables us to prepare for untoward events, improving our chances of curbing them. Likewise, “medical intelligence” – the early diagnosis of diseases, including cancer – can buy information and time, crucial factors that can significantly increase chances of recovery. For this reason, scientists all over the world are striving to develop advanced methods for the early diagnosis of cancer.
 
Prostate cancer is the second most common lethal cancer in men over 60, claiming a quarter of a million lives worldwide each year. There is a need for new methods that can provide reliable and sensitive early detection. Currently, recommended screening for prostate cancer is based on a combination of digital rectal examination, ultrasound and testing the amount of a prostate protein, PSA, in the blood. But these methods are neither sensitive nor reliable enough: Often the tests fail to sound the alarm bells, leaving the cancer to grow undetected, while in a considerable number of cases the tests set off false alarms, flagging benign and non-malignant conditions as potentially cancerous. In addition, these screening tests do not provide information about the exact size or location of the tumor and, worse, they are unable to determine the aggressiveness or clinical stage of the tumor. As a result, many older men are referred for biopsies, which, in as many as three out of four cases, prove negative (though even biopsies can produce false negatives). Because a biopsy is a painful and costly procedure, many scientists worldwide are searching for a non-invasive alternative.
 
Prof. Amos Breskin and Dr. Rachel Chechik, together with Dr. Sana Shilstein and research student Marco Cortesi of the Weizmann Institute’s Particle Physics and Astrophysics Department, in collaboration with Dr. David Vartsky of Soreq NRC, have recently developed a new concept for prostate cancer diagnosis. The method, which begins by detecting prostate zinc levels with X rays, is presently being tested in clinical trials in collaboration with Prof. Jacob Ramon and Drs. Eduard Fridman, Gil Raviv, Alexander Volkov and Nir Kleinman of Sheba Medical Center, Tel Hashomer; as well as Drs. Evyatar Moriel, Monica Huszar, Gabriel Kogan and Valery Gladysh of Kaplan Medical Center, Rehovot.
 
The method derives from three-decade-old observations that the concentration of zinc – an element found naturally and abundantly in healthy prostatic tissue – is low in the prostates of men suffering from advanced prostate cancer. The last decade has brought further insight into the role of zinc in the prostate; it’s involved, among other things, in the secretion of citrate-rich prostatic fluid.
 
The research team wanted to know whether a prostate zinc deficiency could be identified in earlier stages of cancer. They performed a clinical study on about 600 patients who had been referred for biopsies. They then measured the concentration of zinc in the biopsy samples using X-ray-based elemental analysis and compared the results with zinc levels in the blood. The results, which were published in The Prostate, not only showed that lowered levels of zinc in malignant prostate tissue could be detected at very early stages of the disease, they also showed, for the first time, that zinc depletion is positively correlated with tumor aggressiveness: The more aggressive the tumor, the greater the zinc depletion. In contrast, the benign tissue surrounding the tumor contained normal zinc levels. These three findings imply that mapping zinc in the prostate might be a useful way of pinpointing the exact location of a tumor and gauging its aggressiveness.
 
In a subsequent study, published in Physics in Medicine and Biology, the researchers tested whether images of prostatic zinc concentrations could potentially be used in a non-invasive X-ray-screening method. The method was assessed on the basis of computer-simulated images, using zinc concentration values obtained from the clinical trials. By analyzing the images and revealing the regions of depleted zinc, the researchers could not only classify an area as cancerous or benign but also determine the aggressiveness of the cancer as well as its dimensions and location within the prostate gland.
 
On the basis of these results, the team has launched an R&D program to promote the development of a non-invasive, transrectal probe that will generate zinc maps of the prostate gland through X-ray imaging.
 
Chechik: “Although it’s a few years away from production, we hope that the probe will be able to grade the aggressiveness of the tumor as well as indicate whether the cancer might have proliferated to areas outside the prostate gland. This information will help physicians decide whether a biopsy should be performed and significantly increase the sensitivity and accuracy of the biopsy.” Breskin: “The method is designed to help, in the future, in clinical decision making, as well as to be used to guide focal treatments. At the post-treatment stage, the probe could be an effective, non-invasive follow-up tool.”
 

Prof. Amos Breskin’s research is supported by the Helen and Martin Kimmel Center for Archaeological Science. Prof. Breskin is the incumbent of the Walter P. Reuther Chair of Research in Peaceful Uses of Atomic Energy.

(l-r) Marco Cortesi, Dr. Rachel Chechik, Prof. Amos Breskin and Dr. Sana Shilstein. Using medical intelligence
Life Sciences
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Cancer’s Ins and Outs

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Prof. Yosef Yarden and Dr. Yaron Mosesson. Derailing cancer prevention

 

 

 

 

 

 

 

 

 

 

Cancer cells are notoriously versatile survivors that exploit normal cellular machinery to their advantage. Weizmann Institute scientists have recently identified a clever “trick” employed by these cells: Apparently, in many of their survival strategies, cancer cells “derail” a particular mechanism that is crucial to the cell’s functioning. Understanding how such derailment is accomplished could lead to new cancer therapies and help to overcome resistance to existing cancer drugs.
 

The mechanism in question, called endocytosis, serves to introduce substances into the cell: First, the cell’s membrane deforms to create a deep dent, like that in the surface of a rubber ball when it’s pressed with a finger. This dent expands and closes in on itself just underneath the cell membrane, forming a bubble that detaches and is transported to various locations inside the cell. A substance enclosed within the bubble – for example, a nutrient or a receptor molecule – can move in this manner from the cell’s surface into its interior. Ultimately, most substances transported in such bubbles are recycled or destroyed in an organelle called the lysosome.
 
Research by Prof. Yosef Yarden of the Weizmann Institute’s Biological Regulation Department, together with his former graduate student Dr. Yaron Mosesson and other colleagues at Weizmann and elsewhere, suggests that derailed endocytosis facilitates cancer development at different stages. For example, when the inner lining of the lungs or milk ducts is undergoing renewal, endocytosis periodically eliminates the receptors for growth-stimulating molecules, called growth factors, on the cell’s surface. These receptors are sucked into a bubble to be destroyed inside the lysosome, preventing abnormal cellular growth. But if endocytosis is deficient, these receptors can turn into cancer-causing machines: They continue to convey growth signals, leading to carcinoma of the lung, breast or other organs. Overly active endocytosis, on the other hand, can also lead to cancer by destroying the molecular “glue” that holds cells together and prevents them from proliferating excessively. Likewise, in metastasis – the deadly spread of cancer throughout the body – abnormal endocytosis plays an important role: It eliminates the cancer cells’ attachment to tissues, allowing them to migrate and spread.
 
But how exactly is endocytosis derailed? In a study published in Developmental Cell, Mosesson and other members of Yarden’s team, in collaboration with Tel Aviv University, the Technion – Israel Institute of Technology and the University of Porto in Portugal, have identified a previously unknown component of endocytosis in human beings. The molecule, a protein called Lst2, facilitates the endocytosis of growth factor receptors. When Lst2 is lacking, these receptors fail to complete the process, getting trapped in a cancer-promoting routine: They evade the lysosome and move back to the cell surface, where they can start another cycle of growth.
 
A better understanding of endocytosis might help develop new drugs that would block cancer at various stages. Such understanding could also help improve the penetration of existing drugs into malignant cells, thereby overcoming tumor resistance to certain forms of chemotherapy.

 

Prof. Yosef Yarden’s research is supported by the M.D. Moross Institute for Cancer Research; the Aharon Katzir-Katchalsky Center; the Goldhirsh Foundation; and the estate of Benjamin Bernstein. Prof. Yarden is the incumbent of the Harold and Zelda Goldenberg Professorial Chair in Molecular Cell Biology.
 
(l-r) Prof. Yosef Yarden and Dr. Yaron Mosesson. In the bubble
Life Sciences
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Cancer Matters

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Prof. Moshe Oren and Yaara Ofir Rosenfeld. mechanisms of cancer growth
 
 

 

Israel Prize winner Prof. Moshe Oren: "We won't allow the tumor to escape the therapy"


Cocktails. That's the key word in the future fight against cancer, says Prof. Moshe Oren of the Weizmann Institute's Molecular Cell Biology Department, a pioneer of research into the molecular mechanisms of cancer. Advanced medicine will be customized on the basis of a patient's individual genetic profile. If a malignant disease is diagnosed, physicians should be able to prescribe effective treatments with a high likelihood of a cure. Oren, winner of the 2008 Israel Prize, believes these future cancer treatments will consist of a blend of several drugs, similar to the antiviral cocktails that currently keep AIDS at bay. "No single cancer therapy will probably work sufficiently well, and even if it does, the tumor might develop resistance to the drug," he says. "But if the patient receives drugs targeting two different mechanisms, the tumor is much less likely to 'escape' this onslaught."
 
The major advantage of personalized, molecular drugs is fewer and weaker side effects: These therapies will kill the tumor without killing the patient. But how will the drugs be tailored to each patient's needs? Says Oren: "The drug cocktail will target the dominant genetic defects in each person's cancer. Hopefully, we won't have to invent the cocktail each time from scratch but will identify groups of people that respond to certain drug combinations, based on their particular genetic makeup. The right patients should get the right drugs at the right time, as people with cancer often don't get a second chance."
 
A number of molecular therapies currently tested in clinical trials are based on Oren's research into p53, the tumor suppressor gene that is most frequently altered in human cancers. The p53 gene is known as the "guardian of the genome" because it puts the brakes on cancer when the cell's genome is damaged. When these "brakes" are not functioning properly, the road to cancer remains open. In 1983, together with collaborators, Oren was the first to isolate and clone p53, and in subsequent years, he made major discoveries about the way p53 works in normal and cancerous cells. Here he discusses the latest developments in p53 research, including his own most recent findings.
 

Therapies based on p53

 
"We now know that in the vast majority of cancerous tumors the tumor suppressor function of p53 is at least partially defective; but the nature of the defect varies greatly from one tumor to another. In about half of all cancers, the p53 gene itself is directly impaired. In such cases, the most appealing treatment strategy, now tested in clinical trials in China, is to deliver working p53 copies to cells by gene therapy. In other cases, the defect lies either in the genes controlling p53 or in the molecular machinery p53 uses to exert its effects – 'upstream' or 'downstream,' as the scientists say, from p53. In these instances, the therapy is aimed at correcting the defect in order to allow p53 to perform its cancer-blocking function.
 
"About ten years ago, we discovered one crucial 'upstream' mechanism: a genetic switch called Mdm2 that controls p53 activity. Mdm2's job is to make sure p53 is present in the cell in just the right amount by continuously destroying surplus p53 protein. If Mdm2 becomes overly active, it might destroy too much p53, depriving the cell of a vital tumor suppressor mechanism. Such excessive activity of Mdm2 is found in 10% to 20% of all cancers, particularly in sarcomas and in certain types of leukemia. Drugs that block Mdm2 so as to prevent an overzealous destruction of p53 are currently in Phase I clinical trials in the United States."
 

News from the battlefront

 
"In a recent study published in Molecular Cell and conducted in collaboration with researchers in the U.S., we discovered a previously unknown mechanism by which Mdm2 can dangerously decrease the amount of p53 in the cell. We found that Mdm2, in addition to binding directly to p53 and driving its destruction, can reduce p53 levels indirectly – by countering a protein called L26, which plays a pivotal role in p53 synthesis. In other words, Mdm2 can both inhibit the production of the p53 protein and accelerate the demise of the protein that has been produced.
 
"Before we can tell if this finding could lead to a new drug, scientists must determine whether the binding site between the two molecules, Mdm2 and L26, is structurally a good drug target. If it is, I could envision a drug cocktail that would target two separate mechanisms involving Mdm2 – the one we discovered more than ten years ago and the new, indirect one we discovered recently."
 

The origins of complexity

 
"Surely, nature didn't devise several control mechanisms for p53 synthesis just to frustrate cancer researchers. Its goal is to keep p53 levels low when all is well, but to raise them rapidly and efficiently when cancer-causing changes occur in the cell. It's difficult to achieve such a rise with a single mechanism."
 

The challenges ahead

 
"Most new-generation drugs for treating cancer are directed at signaling enzymes, which have been extensively studied. These enzymes include receptors that often are easily accessible on the surface of cells, particularly through the use of specific antibodies. In contrast, p53 operates in the cell nucleus, which is more difficult to reach and must be targeted with specially designed small molecules."
 
Prof. Moshe Oren's research is supported by the Robert Bosch Foundation.
 
 
 
Prof. Moshe Oren and Yaara Ofir Rosenfeld. Guarding the guardians
Life Sciences
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Two Arms Are Better than One

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Prof. Yosef Yarden and Sara Lavi. mechanism for cancer metastasis

 

 

 

 

 

 

 

 

 

 

 

When cancer metastasizes, the tumor cells begin to migrate through the bloodstream and establish secondary growth in other organs. Metastasis is the main cause of cancer death, and understanding the mechanisms that make cells detach themselves from their surroundings and migrate may be crucial to developing treatments to prevent or arrest this stage of cancer.

 
Prof. Yosef Yarden of the Biological Regulation Department led a team of scientists from the Weizmann Institute and the Chaim Sheba Medical Center, as well as Portugal and the U.S., in deciphering a crucial mechanism that controls the first stage of breast cancer metastasis, when the cancer cell first starts to move. This action begins with a signal that comes from outside the cell telling it to prepare for the journey. The signal, called a growth factor, initiates a series of changes in the cell: The cell's internal skeleton comes apart, and the densely packed protein fibers that make up the skeleton unravel to form thin threads that push the cell away from its surroundings.
 
Yarden, Drs. Menachem Katz, Ido Amit and Ami Citri of the Biological Regulation Department; Tal Shay, a student in the group of Prof. Eytan Domany of the Physics of Complex Systems Department; Prof. Gideon Rechavi of the Sheba Medical Center at Tel Hashomer and others set about investigating the protein changes that growth factor signals bring about. They mapped all of the changes in gene expression that take place once the signal is received.
 
As they sifted through huge quantities of data, including every protein level that went up or down, the team noticed one family of proteins that stood out. To the scientists' surprise, one member of this family rose dramatically, while another closely related protein dropped off.
 
Tensins, as these proteins are called, stabilize the cell's internal skeleton. When the team investigated the two proteins, they discovered a significant difference: One of the proteins has two arms, while the other has only one. The two-armed protein – whose level drops in response to the growth factor – stabilizes the cell's structure by grabbing the internal skeleton with one arm and the cell membrane with the other. The one-armed version, in contrast, attaches only to the cell membrane, leaving the protein fibers that make up the skeleton dangling. These unanchored fibers loosen to form the threads that push cells apart. For a cancer cell, this can be the beginning of metastasis.
 
Further experiments were conducted, both on genetically engineered cells and on tissue samples taken from patients with inflammatory breast cancer (a swift and deadly cancer associated with elevated growth factor activity), as well as on samples from cancer patients who had received a drug that blocks growth factor receptors on cell walls. These studies confirmed the ties between the growth factor signal, the levels of the two proteins, and their direct involvement in metastasis.
Dr. Menachem Katz. One-armed protein promotes cancer spread
 
Yarden: "The mechanism we identified can predict the development of metastasis and possibly how the cancer will respond to pharmaceutical treatment." This discovery may, in the future, aid in the development of drugs to prevent metastasis in breast or other cancers.
 
Also participating in this research were Sara Lavi, Nir Ben-Chetrit, Gabi Tarcic, Dr. Moshit Lindzen and Roi Avraham from Yarden's group; Dr. Ninette Amariglio and Dr. Jasmine Jacob-Hirsch from Rechavi's group at Sheba Medical Center; from Portugal, a research team from the Institute of Molecular Pathology and Immunology and the Medical Faculty at Porto University; and from the U.S., Dr. Sarah Bacus and her team at Targeted Molecular Diagnostics (Westmont, Illinois); and researchers from the University of California at Davis, Boston University and GlaxoSmithKline, North Carolina.
 
Prof. Yosef Yarden's research is supported by the M.D. Moross Institute for Cancer Research; the Goldhirsh Foundation; and Mr. Daniel Falkner, UK. Prof. Yarden is the incumbent of the Harold and Zelda Goldenberg Professorial Chair in Molecular Cell Biology.
 

Leading the Invasion

Colorectal cancer is one of the most prevalent cancers in the Western world. The tumor starts off as a polyp but turns into an invasive and violent cancer, which often metastasizes to the liver. In an article recently published in the journal Cancer Research, Prof. Avri Ben-Ze'ev and Dr. Nancy Gavert of the Weizmann Institute's Molecular Cell Biology Department reveal mechanisms involved in the spread of this cancer.
 
In a majority of cases, colorectal cancer is initiated by a key protein – beta-catenin. One of the roles of this protein is to enter the cell nucleus and activate gene expression. In colorectal and other cancers, beta-catenin over-accumulates in the cell and inappropriately activates genes whose expression leads to cancer.
 
Prof. Avri Ben-Ze'ev. player in metastasis
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Surprisingly, one of the genes activated by beta-catenin in colorectal cancer cells is a receptor previously detected by Ben-Ze'ev's group called L1-CAM, which is usually found on nerve cells, where it plays a role in nerve cell recognition and motility. What is this receptor doing on cancer cells? Previous research by Ben-Ze'ev showed that L1-CAM is expressed only on some cells located at the invasive front of the tumor tissue, hinting that L1-CAM could be an important player in the development of metastasis.
 
Using a mouse model for metastasis to check this assumption, the scientists found that colorectal cancer cells engineered to express the L1-CAM gene do indeed spread to the liver, while those cells lacking L1-CAM do not.
 
In collaboration with Prof. Eytan Domany and research student Michal Sheffer of the Institute's Physics of Complex Systems Department, Ben-Ze'ev then compared the expression of genes induced by L1-CAM in cultured colon cancer cells to those in 170 samples of colorectal cancer tissue removed from patients and in 40 samples of normal colon tissue. Out of about 160 genes induced by L1-CAM, some 60 were highly expressed in the cancerous tissue but not in normal colon tissue. Ben-Ze'ev is conducting further research into the role of this set of genes to unravel the details of L1-CAM's function in metastasis.
 
Prof. Avri Ben-Ze'ev's research is supported by the Jean-Jacques Brunschwig Fund for the Molecular Genetics of Cancer; Curie–Weizmann; and the Eugene and Delores Zemsky Charitable Foundation Inc. Prof. Ben-Ze'ev is the incumbent of the Samuel Lunenfeld-Reuben Kunin Chair of Genetics.
 
 
Prof. Yosef Yarden and Sara Lavi.
Life Sciences
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Stem Cells and Cancer

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Givol and Gal. Identifying cancer stem cells

 

 

 

 

 

 

 

 

 

 

 

 

 

Ventures that hold the most promise often present the greatest risk. Stem cells, for instance, with their talent for self-renewal and the potential to turn into any kind of cell, hold the promise of curing any number of diseases. But researchers have discovered in recent years that the risk of developing cancer is intimately tied to the promise of stem cells.

 
Adult stem cells, which are specific to each tissue type, function to maintain the body’s organs over the course of a lifetime, creating new cells to replace dead ones. Like their embryonic cousins, adult stem cells can renew themselves endlessly, and the process of differentiation, in which cells take on the characteristics of specific tissues, is inhibited. However, these exact properties make stem cells good candidates for turning cancerous. Recent theories propose that when an adult stem cell mutates, it can lose some of its properties of self-control while retaining its propensity for self-renewal – a dangerous combination that may lead to cancer.
 
In the past decade, scientists have discovered small amounts of stem cells, dubbed cancer stem cells, in many different types of cancer, including leukemia, breast cancer and brain tumors. These, they believe, are responsible for the continuous growth and post-treatment relapse of the cancer. Cancer stem cells are often especially resistant to standard chemotherapy drugs; they may survive treatment and eventually renew the cancer.
 
How, then, can cancer stem cells be targeted and destroyed? Recent research by Prof. David Givol and research student Hilah Gal of the Molecular Cell Biology Department, carried out together with Prof. Tsvee Lapidot of the Immunology Department and Prof. Eytan Domany of the Physics of Complex Systems Department, aimed to see what distinguishes cancer stem cells from other cancer cells and from healthy stem cells. Also participating in the research were Prof. Gideon Rechavi and his research team from the Sheba Medical Center, Tel Hashomer.
 
Upon comparing levels of gene expression in leukemia stem cells with those of non-stem leukemia cells, the scientists found about 400 genes that are expressed differently in the two types of cancer cell. In the cancer stem cells, for instance, certain genes involved in repairing mistakes in DNA were less active, possibly explaining the fact that these cells are more liable to accumulate harmful mutations. The team then compared the expression patterns of these 400 genes to those of healthy blood stem cells. About a third of them were common to both.
 
The trick now is to examine the patterns that distinguish the cancer stem cells from normal ones. If important patterns of activity that are unique to cancer stem cells can be identified, a way might be found to block these functions in the cancer stem cells without harming healthy adult stem cells. The team discovered that over half of the genes in cancer stem cells are expressed differently from those of adult stem cells, and these will hopefully provide a starting point in the search for promising drug targets. 
   
Prof. Eytan Domany’s research is supported by the Clore Center for Biological Physics; the Kahn Family Research Center for Systems Biology of the Human Cell; the Yad Abraham Research Center for Cancer Diagnostics and Therapy; the Ridgefield Foundation, New York, NY; the Wolfson Family Charitable Trust; and Mr. and Mrs. Mordechai Segal, Israel. Prof. Domany is the incumbent of the Henry J. Leir Professorial Chair.
 
Prof. Tsvee Lapidot’s research is supported by the Helen and Martin Kimmel Institute for Stem Cell Research; the Belle S. and Irving E. Meller Center for the Biology of Aging; the Gabrielle Rich Center for Transplantation Biology Research; the Crown Endowment Fund for Immunological Research; and the Charles and David Wolfson Charitable Trust. Prof. Lapidot is the incumbent of the Edith Arnoff Stein Professorial Chair in Stem Cell Research.
 
Prof. David Givol and research student Hilah Gal. Differences in expression
Life Sciences
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Predicting Success

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(l) Mapping the concentration of a contrast material (simulating a drug) inside the tumor. (r) A mathematical interpreation that "translates" the concentration data into areas of different pressure inside the tumor. the lower the pressure, the greater the concentration.
 
Chemotherapy drugs given intravenously are the mainstay of the fight against cancer. But while these drugs sometimes effect a complete cure, other times they can be almost ineffective. A team headed by Prof. Hadassa Degani of the Biological Regulation Department has come up with a non-invasive method for predicting possible problems. The findings of their studies on animals, which appeared in Cancer Research, may in the future influence treatment regimes for millions of cancer patients. 

Intravenous infusions rely on the bloodstream to carry drugs to where they are needed. Normally, a material such as a chemotherapy drug crosses into a tissue on the principle of concentration equalization – the material diffuses from an area of high concentration to one of low concentration until the concentrations become equal all around. In some cancers, however, even though the material “wants” to spread out evenly, fluids inside the tumor may be exerting pressure, preventing the drug from entering.

The method the Institute scientists developed can measure, with a non-invasive magnetic resonance imaging scan, whether the fluid pressure in the cancerous tissue is at a level that could render chemotherapy ineffective. Degani says that, ideally, the fluid pressure inside the tumor tissue would be checked before a patient begins chemotherapy. If the pressure were discovered to be high, it might be possible to reduce it by various means. The method, if it proves successful in clinical trials, might have the potential to significantly increase the success rate of chemotherapy.  
 
Prof. Hadassa Degani’s research is supported by the M.D. Moross Institute for Cancer Research; the Willner Family Center for Vascular Biology; the Washington Square Health Foundation; Lord David Alliance, CBE, UK; Dr. and Mrs. Leslie Bernstein, Sacramento, CA; Ms. Lynne Mochon and the estate of Edith Degani, New York, NY; Ms. Sophy Goldberg, Israel; and the estate of Julie Osler, New York, NY. Prof. Degani is the incumbent of the Fred and Andrea Fallek Professorial Chair in Breast Cancer Research.
(l) Mapping the concentration of a contrast material (simulating a drug) inside the tumor. (r) A mathematical interpreation that "translates" the concentration data into areas of different pressure inside the tumor. the lower the pressure, the greater the concentration.
Life Sciences
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DNA Computer Might Fight Cancer

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Prof. Ehud Shapiro and his team. Future vision of medicine

Following a newsworthy debut several years ago at the Weizmann Institute, it’s once again making headlines. The world’s smallest computer - a drop of water can hold around a trillion - has now been programmed to perform actions more often associated with doctors than computers: to diagnose and treat cancer.


The computing device successfully identified signs of cancer introduced into a test tube environment, diagnosed the type of cancer and even released an appropriate drug.


Prof. Ehud Shapiro of the Departments of Computer Science and Applied Mathematics and of Biological Chemistry, his research students - Yaakov Benenson, Binyamin Gil and Uri Ben-Dor - and Dr. Rivka Adar have made a splash in the scientific community with their futuristic vision of a “doctor-in-a-cell” that might one day be able to diagnose and treat disease from within, before symptoms even appear. Their study recently appeared in Nature and was presented at the prestigious “Life, a Nobel Story” symposium in Brussels.


The team programmed their computer to detect prostate cancer and one form of lung cancer. The computer evaluates four genes that become either under- or overactive once the disease sets in. The chosen genes control the expression of messenger RNA (mRNA), which carries information from the nucleus to the ribosome, the cell’s protein factory. The scientists introduced different levels of these RNA molecules into the test tube to simulate the presence or absence of cancer.


Made entirely of biological molecules, the computer has three components - input, computation and output. The first consists of short strands of DNA, called transition molecules, which check for the presence of the mRNA produced by each of the four cancer genes. The second component is a computation (diagnostic) unit, consisting of a long hairpin-shaped DNA strand. As the computer’s input segments check for the presence or absence of the four cancer markers, this diagnostic unit checks each input in turn, producing a positive diagnosis of malignancy only if all four markers point to cancer.


This second component also contains the computer’s third component: a single-stranded DNA known to interfere with the cancer cell’s activities. In the case of a positive diagnosis, the unit releases its hold on the therapeutic unit, activating its cancer-fighting potential.


But there’s an added safety feature: if the activity of even one of the four genes is normal (as determined by the test tube levels of the mRNA marker it codes for), the diagnosis is “not cancerous,” and the computer releases a different strand of the computer’s DNA that neutralizes the drug.


The original version of the bio-molecular computer (also in a test tube) was created by Shapiro and colleagues in 2001. This computer was capable of performing mathematical operations such as checking a list of zeros and ones and ascertaining whether all of the zeros precede all of the ones, or whether there is an even number of ones in the list. An improved system, which uses its input DNA molecule as its sole source of energy, was reported in 2003 and was listed in the 2004 Guinness Book of World Records as the smallest biological computing device.


Shapiro: “Our study offers a vision of the future of medicine. It is clear that it may take decades before such a system operating inside the human body becomes a reality. Nevertheless, only two years ago we predicted it would take 10 years to reach where we are today.”

cartoon: New meaning to "computer virus"

Prof. Shapiro’s research is supported by the Samuel R. Dweck Foundation; the Dolfi and Lola Ebner Center for Biomedical Research; the M.D. Moross Institute for Cancer Research; the Benjamin and Seema Pulier Charitable Foundation and the Robert Rees Fund for Applied Research.

 

 
(l-r) Uri Ben-Dor, Prof. Ehud Shapiro, Yaakov Benenson, Dr. Rivka Adar and Binyamin Gil. Doctor-in-a-cell
Life Sciences
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Reversing Colon Cancer

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Prof. Avri Ben-Ze’ev. Tracing cell circuitry

 

Weizmann Institute scientists have uncovered a key mechanism leading to the spread of cancerous colon cells and have succeeded in reversing their metastasis in laboratory tests. The study, published in the Journal of Cell Biology, raises hopes that target-specific drugs might be devised to prevent, or reverse, the metastatic stage of colon cancer.


The second most prevalent type of cancer in men and the third in women in the Western world, colon cancer is lethal largely because its cells spread to a variety of other tissues, primarily the liver.

Normal cell growth and repair are orchestrated through an intricate checks-and-balances system controlled by a circuitry of genes and their respective proteins. Tumor formation is generally triggered by a mutation in one or several of these genes, causing the circuitry to go off track.


The team of Institute researchers headed by Prof. Avri Ben-Ze’ev of the Molecular Cell Biology Department has now traced one of the key cellular circuitries that, when mutated, leads to metastatic cancer of the colon. Its main players are two “cell-gluing” molecules known as beta-catenin and E-cadherin, and a cancer-causing gene called Slug. The team showed that the malfunction of these adhesion-related molecules causes the cancer cells to break loose from the tissue and migrate to form another tumor at a distant site.


They found that abnormally high levels of beta-catenin (due to a mutation in the beta-catenin gene itself or in one of the genes controlling its breakdown) cause a surge in Slug, which then inhibits the production of beta-catenin's partner in cell adhesion, E-cadherin. The resulting E-cadherin shortage prevents the cell from adhering to adjacent cells. “The cell takes on a boat-like shape and, leaving the pack, enters the bloodstream and migrates to distant colon tissue, where it proceeds to multiply, forming a new tumor,” explains Ben-Ze’ev.

 

Drug for Slug

The scientists found that when colon cancer cells are surrounded by other such cells in the crowded environment created in a test tube, minute quantities of E-cadherin recruit beta-catenin from the nucleus and bind to it. Lower levels of beta-catenin in the nucleus then result in decreased Slug production, leading, in turn, to increased E-cadherin production. As a result, the cells stick together and form a tissue-like organization, losing their invasive properties. This finding parallels a recent study in colon cancer patients by pathologists at Erlangen University in Germany. In examining lymph node tumors that had spread from the patient’s colon, the researchers found that some of the cells naturally maintained their invasive character, while others reordered into a crowded, normal “tissue-like” organization. Something about their new environment induced cell repair. This is precisely the process that Ben Ze’ev’s team hopes to promote to block metastasis. The question is how to tilt the scales in favor of the formation of normal tissue.


 “The fact that the invasive process in colon cancer can be turned around is surprising,” says Ben-Ze’ev. “It offers hope of reversing the metastatic process, or even preventing it, in the future. One idea would be to design a drug that would raise the levels of the adhesive E-cadherin protein by targeting its inhibitor - Slug.”  


Prof. Ben-Ze’ev’s research is supported by the M.D. Moross Institute for Cancer Research; the Yad Abraham Center for Cancer Diagnostics and Therapy; the estate of Maria Zondek; and La Fondation Raphael et Regina Levy. He is the incumbent of the Samuel Lunenfeld-Reuben Kunin Professorial Chair of Genetics.

Slug reduces represses cell gluing protein

 
 
 

 

Prof. Avri Ben-Ze’ev. Silence of the genes
Life Sciences
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